Carpenters, during the normal course of their work, face a variety of different construction tasks. Many of these tasks require different lengths and sizes of leveling and squaring tools. Understandably, various carpenters tools have been developed that serve to reduce the number of such tools required, and thereby make it easier for the carpenter to transport and use such tools. For example, extensible levels exist in the prior art that are useful for tasks requiring either a short or long level. Such extensible level prior art is found, for instance, in U.S. Pat. 747,850, issued to Bihlman on Dec. 22, 1903; U.S. Pat. 1,403,676 to Eltag et al. on Jan. 17, 1922; U.S. Pat. 1,413,056 to Parrish on Apr. 18, 1922; U.S. Pat. 2,879,606 to Olivere on Mar. 31, 1959; and U.S. Pat. 4,607,437 to McSorley, Sr. et al. on Aug. 26, 1986. Such prior art devices, however, are not well suited for working with surfaces that are non-linear, such as corners and other 90.degree. and 45.degree. angled surfaces. Such devices cannot function, for example, as T-squares or a right-angle rule. Further, such prior art devices are considerably weaker in their extended configuration than in their compact configuration. As a result, such devices are more prone to damage in their extended positions, and it is well known that tools at construction cites often experience many harsh, potentially damaging forces. Moreover, relatively little force is required to bend the various sections of such extended devices out of linear alignment, resulting in erroneous measurements and readings. Further, such devices are either limited to a maximum extension length or cannot provide an extended contiguous working surface.
Clearly, then, there is a need for a carpenter's tool that is useful for leveling across short and arbitrarily long distances. Such a needed device would be durable, relatively easy to manufacture, and remain straight over large distances. The linearity of such a device, moreover, could be verified at multiple points along its length. Such a needed device, further, could be quickly adapted for use as a T-square, a right-angle rule, or other measuring and leveling tools. Still further, such a needed device would be collapsible and, when collapsed, would fit into a standard tool box. Still further, such a needed device would be easy to use and adapt to various configurations. The present invention fulfills these needs and provides further related advantages.